DE-A 44 05 342 discloses a continuously operating press and a method of controlling the press force on press heating plates within the press length of an operating cycle in the production of particle boards, fiberboards and similar wooden-material boards, and also of plastic sheets. The object of DE-A 44 05 342 is to provide a continuously operating press which makes it possible, longitudinally and transversely along the pressing path between the upper and lower press heating plates, to control or adjust hydro-mechanically a change in the press nip distances both in the idling mode prior to entry of the material to be pressed (start-up mode) and also in loaded mode during production, using an on-line method in a few seconds. The solution provided has proved workable in practice.
The significant part of this solution is the elastic-non-positive suspension or connection of the upper press heating plate to the upper press ram, which can be flexibly controlled hydro-mechanically, and the elastic non-positive suspension or connection of the lower press heating plate to the lower, stationary press table, on which one or more hydraulic short-stroke plunger cylinders per press column or press frame structure are arranged transversely, centrically with respect to the convex bending deformation.
By means of this continuously operating press, the longitudinal bending deformation of the upper press heating plate in the relaxation section b+c+d of the pressing path L, particularly as required in the production of fiberboards (MDF), having steep deformation gradients (decompression angle .beta..sub.1 and compression angle .beta..sub.2) can be controlled hydraulically by means of mechanical actuating mechanisms on any desired press section along the pressing path L. However, the structure of these mechanical actuating mechanisms is expensive.